1. Field of the Invention
This invention relates to a hollow rail or bar for a fabric covering for an architectural opening, such as a bottom rail for a fabric roller blind or a top or bottom rail for a roman shade, and a method for attaching the fabric of the covering to the rail.
2. Description of the Relevant Art
Profiles for elongate hollow bottom rails for fabric window coverings are known, for example, from: GB 1,191,532, GB 1,366,961, GB 1,462,613 and JP 63-24786. Often, such bottom rails are cut from a length of hollow, extruded plastic or hollow, roll formed or extruded metal and are of round, elliptical or generally pear shaped cross-section. The interior of such a bottom rail often has had a continuous intermediate widthwise cross web, extending between the rail's walls on its opposite widthwise sides and dividing the inside of the rail's profile into upper and lower portions extending along the length of the rail. The upper portion has usually had a lengthwise opening or slot in the top of the rail, and in some window coverings, the lower portion has also had a lengthwise opening in the bottom of the rail. A marginal end of the fabric of a window covering has generally been inserted in such a lengthwise opening in a bottom rail to attach the fabric and rail together.
One method of attaching a fabric to such a rail has involved providing the marginal end of the fabric with a stiffening (e.g., stiff plastic) member that extends along the length of the rail. The marginal end of the fabric with the stiffening member has been inserted into an end of the rail, above or below the rail's cross web, and then slid lengthwise along the cross web as the remainder of the fabric, extending through the rail's upper or lower lengthwise opening, is slid along the rail's lengthwise opening. The stiffening member has held the marginal end of the fabric within the upper or lower portion of the rail, into which the stiffening member has been inserted, and prevented the marginal end of the fabric from subsequently being pulled out of the rail, through its adjacent lengthwise opening in the rail's upper or lower portion. In a rail where the width of the stiffening member has been smaller than the width of the adjacent lengthwise opening in the rail's upper or lower portion, the interior of the upper and/or lower portion has been provided with a lengthwise locking shoulder, which can engage the stiffening member to prevent it from being pulled out of the adjacent lengthwise opening.
Another method for attaching the fabric and rail, as described in U.S. Pat. No. 3,018,824, has involved providing clips within a lengthwise opening or groove in the rail's upper or lower portion. In this method, a creasing device has been used for inserting the fabric into the lengthwise opening and a clip driver has been used for subsequently inserting locking clips into the opening. The creasing device has used an elongated blade to push the fabric into the opening in a single operation. The clip driver has used a wheel to push the fabric into the opening as the wheel is rolled along the length of the opening.
Yet another method for attaching a screen fabric to each side of a frame, as described in U.S. Pat. No. 5,127,143, has providing a spline in a shallow lengthwise groove in each side of the frame. In this method, a wheel has been rolled over both the screen fabric and the spline, lain atop the groove, to insert the screen fabric and spline into the groove.